When a new subscriber unit attempts to access a wireless communication network, the subscriber unit determines the frame/symbol boundary of the downlink transmission, compensates for frequency offset, and identifies the base station ID (i.e., the cell ID). This process is generally referred to as initial synchronization. As those skilled in the art will appreciate, the initial synchronization of Mobile WiMAX (Worldwide Interoperability for Microwave Access) signals based on the IEEE 802.16e standard poses challenges different than those observed in other orthogonal frequency-division multiplexing (OFDM) systems such as wireless local area networks (WLANs) and digital video broadcasting (DVB) systems.
Some of the challenges may include low operating signal-to-noise ratios (SNRs), non-ideally repetitive structure in the preamble, multipath contaminated cyclic prefix, a large number of possible cell IDs, and potentially large frequency offsets. Generally, a low SNR affects the reliability of energy gap detection, and a non-ideally repetitive structure in the preamble causes great performance loss in auto-correlation detection. Furthermore, multipath contaminated cyclic prefix reduce the effectiveness of cyclic prefix based detection, and the large frequency offsets coupled with the number of cell IDs creates a significant computational burden for cross-correlation.
Those skilled in the art will appreciate that there is a need for optimized systems and methods for initial synchronization in a communications medium, such as, but not limited to, a wireless network whereby computational resources are efficiently utilized. The wireless network may conform, for example, to the Mobile WiMAX (IEEE 802.16e) standard.